In the UK, I understand that a SCAVENGER is someone who disposes of rubbish, garbage, etc.

In the USA, a SCAVENGER is often someone who looks for useful things among apparently discarded items.  A SCAVENGER could collect aluminum cans, copper wire, or cardboard for recycling.  In the military a SCAVENGER may be a soldier/sailor very successful at finding (stealing?) extra ammunition, gasoline, air conditioners, steaks, beer, vehicles, etc.

A SCAVENGER can also be someone playing "Scavenger hunt".  In the game, participants are given a list of things that must be found and be taken to a special place within, let's say, two hours.  When the teams return, they compare what they have brought with the list provided by the host.  A typical list might include:

1-a blue crayon

2-a glass of water

3-a partially eaten donut

4-a foreign language dictionary

5-a car part

6-an earring

7-a leaf

8-a menu

9-a book of matches

10-sunglasses

These games are lots of fun!